Underfloor air distribution has gained popularity in work environments due to its design flexibility and reconfiguration capabilities. While early underfloor air distribution systems were designed for spaces housing large computer systems, the increased use of local area networks and telecommunication systems are requiring entire buildings to be designed with underfloor air distribution systems that provide large quantities of cooling air. Also, with the trend to more frequent office reorganization, flexible offices with electrical and mechanical systems that can be easily reconfigured at minimum cost to accommodate personnel and hardware requirements are in increased demand.
Bottom source or underfloor air distribution systems typically include a number of small diffusers that can be moved to accommodate frequent changes in space usage and the resulting changes in ventilation requirements. The diffusers are typically mounted in a raised floor that defines the top surface of a plenum chamber. In other words, the space beneath the floor panels constitutes an enclosed plenum chamber or air space in which the air pressure is greater than in the room or other enclosure to be heated, cooled or ventilated. Air flows from the plenum chamber through the diffusers into the room or other enclosure. For optimal performance, diffusers should expel air in a swirling air pattern with little or no turbulence and, to prevent drafts, relatively low jet velocities. This pattern promotes high induction or entrainment rates that mix unconditioned air within the room with the air being supplied through the diffusers, thereby providing comfortable air movement and eliminating or reducing air stagnation and stuffiness.
One known underfloor air distribution system, produced by Krantz, is an injection molded device consisting of a diffuser grille, a damper, a basket, a trim frame and a retaining frame. The damper is placed within the basket, and the diffuser is placed on top of the basket. The basket is inserted into the trim frame, which is inserted into the retaining frame. The retaining frame, in turn, can be affixed to flooring panels for access to the underfloor air plenum supply. The grille is designed with a circular configuration and has air slots which extend radially from the center of the grille to the outside edge of the grille. The slots can vary in length and width, but have a uniform slope.
Typical underfloor air distribution systems, such as those produced by Krantz, are difficult to manufacture due to the intricate nature of the grilles. Currently, grilles manufactured from a composite material are produced in injection-type molds with retractable core pins that form the intricate pattern of slots in the grille. After molding, each core pin must be retracted from the grille so that the grille can be removed from the mold. This adds a significant increment of time, perhaps 50 to 100%, to the time that would be required to produce the grille if it could be produced on a solid mold with fixed core pins. The retractable core pins also multiply the costs to produce and maintain the equipment. The costs for molds for previous diffuser grilles, with retractable core pins, has been estimated to be at least $500,000, whereas a solid mold for producing the same grille, if this could be done, might cost less than $100,000. The retractable core pins also increase the maintenance costs substantially. With all off these costs and disadvantages, molds with retractable core pins would normally be considered cost prohibitive for this type of diffuser. Thus, to reduce equipment cost, manufacturing time and the costs of the molded grilles, there is a need for grille designs, and production equipment and methods, whereby the grille is readily and easily removed from a solid mold with fixed core pins.